Airfoil CL & CD Start at normal magnitude then skyrocket.

t_topt_top Member

I'm working with a few airfoils, NACA 23012, NACA 63015A, NACA 4412, RC4-10, and Boeing VR-7, analyzing the lift, drag and moment of each.


Currently working on the NACA 63015A. Using velocities(mph) with their respective lift/drag/moment coefficients are below.

  • 25mph {-0.900/0.0257/0.0225}
  • 50 {-3.7196/0.881/0.0856}
  • 75 {-8.507/0.182/0.1837}
  • 100 {-15.368/0.30669/0.3003}
  • 125 {-24.249/0.4598/0.444}
  • 140 {-21.468/1.4205/0.8104}
  • 150 N/A


After 25mph both lift and drag are too high. I recently changed to reference values to get the 25mph to be in its normal range.


Airfoils' length are 8.9in = .22606m


Here are the details for the 2D case:

Solver:

Pressure-Based

Steady state

Velocity formulation -> Absolute


Model:

Viscous Model -> Spalart-Allmaras (1eqn)

Vorticity-Based


Fluid:

Air

Density = 1.225 (kg/m^3)

Viscosity = 1.802e-5 (Kg/m-s)


Reference Values changes:

Area = 0.22606

Density = 1.225

Depth = 1

enthalpy = 0

Length = 0.22606

Pressure = 0

Temperature= 288.16

Velocity = varies

Viscosity = 1.802e-5

Ratio of specific heat = 1.4

Yplus for heat tran. coef. = 300


Turbulence

Specification Method -> Turbulent Viscosity Ratio

Ratio = 10


Outlet pressure = 0


Solution Method

Coupled

Gradient -> Least Squares Cell Based

Pressure->Second Order

Momentum -> Second Order Upwind

Modified Turbulent Viscosity -> Second Order Upwind

Pseudo Transient ->off


Solution Controls:

Flow Courant Number = 200 (recently reduced it to 1 after reading up on it.)

Momentum = .5

Pressure = .5

Relaxation factors

Density, Body Force, Turbulent viscosity = 1

Body Forces = .8


Report definitions of drag

x=cos(angle)

y=sin(angle)


Report definitions of lift

x=-sin(angle)

y=cos(angle)


Report definitions of moment

Center

x=1/4 of span

y= location of x in y direction.


ONE LAST THING

The contour graphics are showing the boundaries of the elements instead of a filled in contoured graph.

More pictures are below that may be relevant


Answers

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